發送短信 : Vibration of functionally graded cylindrical shells

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 /_   _//   / _ \\   | |/ //   / _ \\   |__  //  
 `-| |,-   / //\ \\  | ' //   | / \ ||    / //   
   | ||   |  ___  || | . \\   | \_/ ||   / //__  
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   `-`'   `-`   `-`  `-` --`   `---`    `-----`